Discharge tube



Feb. 14, 1933. J. HEUVEUNK 1,897,255

DISCHARGE TUBE Filed March 16, 1929 2 gvwemtoz DIRK J. HEUVELlNK Patented Feb. 14, 1933 UNETEB STATES PATENT OFFICE DIRK JAN HEUVELINK, OF EINDHOVEN, NETHERLANDS, ASSIGNOR TO RADIO CORPORATION OF AMERICA, A CORPORATION OF DELAWARE DISCHARGE TUBE Application filed March 16, 1929, Serial No. 347,505, and. in the Netherlands March 30, 1928.

The invention is concerned with electric discharge tubes, more particularly with those comprising an incandescent cathode and a grid provided with supporting wires.

The term supporting wires is to be understood to include not only thin but also thick wires, the latter being sometimes referred to as supporting rods.

In such di charge tubes the grid supporting wires are often assembled so as to form a rigid unit by being soldered together. This may have certain disadvantages, however, for example, when grid supporting wires consisting of a metal of high melting-point are soldered together with the aid of a metal having a lower melting-point. At the high temperature at which the latter metal is heated during the operation of the tube, occluded gases are set free, the vacuum in the tube being deleteriously affected by these gases. In addition, the soldering metal volatilizes and settles on the wall of the tube, due to which the heat radiation is made diificult.

The invention has for its object to provide a sturdy grid construction whereby the said disadvantages are obviated.

According to the invention, in an electric discharge tube comprising an incandescent cathode and a grid with supporting wires,

at least two of the said Wires consist of a single bent wire. The grid-supporting wires which do not consist of a single wire may be secured at their bent portions to each other with the aid of metal wire. Between the bent portions of the grid supporting wires may be provided an insulating member to which the cathode may be secured, preferably elastically.

The invention will be explained more fully with reference to the accompanying drawing, in which Fig. 1 is a perspective view of part of the grid and the cathode of a discharge tube according to the invention and Fig. 2 is a longitudinal section in the plane of the rod 7.

In the drawing, a grid 1 is helically wound on supporting wires 2, 3, 4:, and 5 made of a metal of high melting-point, for example,

molybdenum. The wires 2 and 5 on the one hand and the wires 3 and 4 on the other hand constitute a single bent wire their bent portions being secured to each other with the aid or? metal wires 6, for example, tungsten and being in efii ect a projecting end of the grid support which extends beyond the upper end of the grid.

Between the bent portions of the grid sup porting wires is clamped an insulating rod '7 which is in eiiect mounted on the projecting end of the grid support and which consists, for example, of glass and on which a filamentary cathode 9 is hung by means of a spring 8.

At the top the grid 1 is covered by a metal disc 10, which is secured to the grid sup porting wires by reason of the fact that under and above the metal disc these wires are slightly pinched. A small circular plate 12 is secured to the spring 8, being arranged over an aperture 11 of the disc 10 and spaced therefrom. The metal disc 10 and plate 12 prevent escape of electrons from the filament through the top of the grid. For this purpose, the plate 12 may be slightly larger than the aperture 11. The spacing between the disc 10 and tile plate 12 permits the heat due to the filament 9 to escape without injuring the filament support.

I claim:

1. In an electron discharge device the combination with a looped filamentary cathode, and a grid surrounding said cathode and comprising support rods and a helix of grid wire on said rods, of a metal disc supported on said rods in position to cover one end of said helix and having a central aperture, an insulating bar mounted on said rods adjacent said disc, a filament support extending through said aperture and secured at one end to said bar, and a metal plate larger than said aperture mounted on said filament support to be over said aperture but spaced away from said disc.

2. In an electron discharge device the combination of a cathode, and a helical cooperating electrode surrounding and coaxial with said cathode and comprising an electrode support with a projecting end which extends beyond one end of said electrode, of a consupport carried on said insulator and pro- 2 i i r 1,897,255

ductive disc secured to and covering said end of sand helical electrode and having a central aperture, an insulator carried by the binationwith a cathode and a helical grid surrounding and coaxial with said cathode and having a grid support projecting beyond one end of said grid, of a metal disc with a central aperture on said end of said grid, an insulator mounted on said grid support adjacent said end of said grid, a cathode j ecting thru the/central aperture of said meta l disc, and a plate larger than said aper tur'e mounted on said cathode support adjacent and spaced away from said metal disc and in registry With the aperture in said disc.

DIRK JAN HEUVELINK.

3. In an electron discharge device the com- 

